[ Upstream commit c1887159eb48ba40e775584cfb2a443962cf1a05 ]
__startup_64() uses fixup_pointer() to access global variables in a
position-independent fashion. Access to next_early_pgt was wrapped into the
helper, but one instance in the 5-level paging branch was missed.
GCC generates a R_X86_64_PC32 PC-relative relocation for the access which
doesn't trigger the issue, but Clang emmits a R_X86_64_32S which leads to
an invalid memory access and system reboot.
Fixes: 187e91fe5e91 ("x86/boot/64/clang: Use fixup_pointer() to access
'next_early_pgt'")
Signed-off-by: Kirill A. Shutemov <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Link:
https://lkml.kernel.org/r/[email protected]
Signed-off-by: Sasha Levin <[email protected]>
---
arch/x86/kernel/head64.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 7df5bce4e1be..29ffa495bd1c 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -184,7 +184,8 @@ unsigned long __head __startup_64(unsigned long physaddr,
pgtable_flags = _KERNPG_TABLE_NOENC + sme_get_me_mask();
if (la57) {
- p4d = fixup_pointer(early_dynamic_pgts[next_early_pgt++],
physaddr);
+ p4d = fixup_pointer(early_dynamic_pgts[(*next_pgt_ptr)++],
+ physaddr);
i = (physaddr >> PGDIR_SHIFT) % PTRS_PER_PGD;
pgd[i + 0] = (pgdval_t)p4d + pgtable_flags;
--
2.20.1
